The present invention relates in general to hydraulic driving systems, and in particular to a system for use in multiple-axle heavy-duty vehicles having drives for respective axles. The system is of the type which includes at least one pump and a plurality of hydraulic motors which are connected in parallel to respective high-pressure and suction ports of the pump.
When hydraulic motors in driving systems of this kind must operate under different loads to overcome different resistances, for example when some of the wheels of the vehicle are on a slippery surface whereas the traction of other wheels is normal, then there is a danger that motors working against the excessive load may run at an unduly low speed or even come to a standstill while practically the entire stream of pressure fluid delivered by the pump is supplied to the motors operating under the negligible load, causing the latter to attain excessive speed. This danger may occur also when the roadway for the vehicle has non-uniform frictional quality, for example when it is partially covered with ice. In this case, the motors pertaining to slipping wheels may also run at excessive speed and are subject to damage or breakdown.